Compact units of this type are prior art. Such units are used for supplying pressure to hydraulic circuits, in particular, when working hydraulics are to be supplied with pressurized hydraulic liquid at locations in which only a limited amount of space is available. When units are required to be operated continuously in cramped locations, as a result, steps have to be taken for cooling the motor and for cooling the hydraulic fluid. The accommodation of the all the components, including hydraulic pump and heat exchanging device in a housing having small dimensions, creates multiple difficulties. For example, difficulties are created when hydraulics of manufacturing machines, such as lathes, must be supplied with pressurized fluid in closed factory buildings.